The present invention relates to a solar dynamic power system and a process for converting solar radiant power to electrical power. It relates specifically to a solar radiation receiver in which a large fraction of the radiation is absorbed directly by the working fluid of a heat engine. This creates new possibilities for increasing the fraction of the solar radiant power that is converted into electrical power. It also creates the possibility of simplifying the system architecture in ways that have numerous advantages.
Solar dynamic power generators have been discussed in Wallin et al., NASA Contractor Report No. 180877, "Solar Dynamic Power System Definition Study," Mar. 1988, prepared for Lewis Research Center under contract NAS3-24864. The above study compares various theoretical solar dynamic systems using established concentrators, receivers, radiators and power conversion technologies. Among the heat engines incorporated in these solar dynamic systems are Brayton, Rankine, pumped-loop Stirling, and heat pipe Stirling cycle engines.
The receiver in the system discussed in the NASA study comprises one of various thermal eutectic salts, and the working fluid is an inert gas such as Helium/Xenon.
The systems proposed in the study have several practical disadvantages. The receiver of the study uses eutectic salts which make up the receiver cavity to directly absorb the concentrated solar radiation. This method of absorption limits the maximum operating temperature of the working fluid and thus also limits the efficiency of the heat engine which converts the absorbed energy to power. Moreover, because the walls of the receiving space absorb the concentrated solar energy, an increase in temperature of these systems would also cause an increase in radiant energy loss from the receiving space.
It is therefore an object of the present invention to provide a receiver for a solar dynamic power system in which a significant portion of the energy input is absorbed directly by the heat engine working fluid which circulates through the receiver cavity.
It is a further object of the present invention to provide a receiver for a solar dynamic power system in which radiant energy loss from the receiver space is prevented.
Another object of the present invention is to provide a receiver for a solar dynamic power system which eliminates hot spots due to aiming errors in the concentrator of the power system.
A still further object of the present invention is to provide a receiver with the smallest possible volume.
Yet another object of the present invention is to provide a receiver which makes it possible to operate at a given turbine operating temperature, for example, with smaller temperature gradients in both the thermal energy storage portion and the receiver.
It is also an object of the present invention to provide a complete solar dynamic power system of improved power efficiency incorporating the receiver of the present invention.
An additional object of the present invention is to provide a complete solar dynamic power system of increased reliability which is easily protected from an external threat.